Anyone in the World ever heard of or diagnosed with Hemaglobin Sabine?

My daughter was born with an autoimmune disorder that is extremely rare called Hemoglobin Sabine. The closest other blood disorder that is similar to hers is Thalassemia and Sickle cell disease. We have had 15 blood transfusions and she's 8. Needless to say, we need some help. She is now, of course, in iron overload and cannot bare having another transfusion. Our only hope is Hydroxyurea. But I am very hesitant. The doctors say the only side effect would be her white blood cell count possibly decreasing. I was reaching out to anyone on here to see of their experiences with this medicine, particularly anyone who has a similar blood disorder as hers, to see their experience with this drug.